1. Field of the Invention
The present invention relates to a focus detecting unit, and a refractive index measuring apparatus and a non-contact thermometer using the same.
2. Description of the Related Art
As a conventional refractive index measuring apparatus, it has been proposed, for example, in Publication of Unexamined Patent Application of Japan, Toku Kai No. 2000-28526.
As a conventional non-contact type thermometer, it has been proposed in Publication of Examined Patent Application of Japan, Toku Kou Hei 5-66976.
That is, a refractive index measuring apparatus for liquid using an Arrayed Waveguide Grating type wavelength multiplexer-demultiplexer (hereafter, it is abbreviated as AWG) is shown in the publication of Toku Kai No. 2000-28526.
In this refractive index measuring apparatus of liquid, the light from a light source 40 is detected as a main wavelength λC0 by a spectrum analyzer, when there is no liquid in a groove 30.
On the other hand, if the groove 30 is filled up with liquid, it is detected as a central wavelength λC1 since phase modulation arises by an amount of the refractive index of the liquid.
The refractive index of the liquid filled in the groove can be calculated by determining the central wavelengths λC0, λC1 of a spectrum detected by this spectrum analyzer.
In a non-contact type thermometer disclosed in the Publication of Examined Patent Application of Japan, Toku Kou Hei 5-66976, an environmental temperature is measured. Here, facts that a quartz substrate on which a diffraction grating is formed is deformed by thermal expansion, and accordingly a lattice constant of the diffraction grating changes are utilized.